I added preferredSize attributes to my nodes which works fine so far. The problem then is when a label is growing larger than the preferredSize.dx attribute of the containing node, this node isn't resizing anymore:

Is there a way to enable the resizing feature of nodes with preferredsize attribute?

Hi Phil,
The label there is places in a Rounded Rectangle(as seen from the picture). Is this right? I faced also this problem and the solution was to use a Custom Figure for this label with the following Qualified Class Name : org.eclipse.gmf.runtime.draw2d.ui.figures.WrappingLabel and as a child I added a Custom Attribute : name - textWrap ; value - true.
This should work in a Rounded Rectangle.
You can use also Insets ( Left 5 , Right 5 ) to let some space until the rectangle line

Just would like to add, that since GMF 3.0, you don't need to use custom figure to allow configuration of non-modeled properties via custom attributes -- all figures now support adding CustomAttributes with the same attribute configuration generated for all cases.

So the standard (non-custom) Label with CustomAttribute {name: textWrap, value: true } should work as well.

Thx for your suggestions. The CustomAttributes hasn't worked for me, because of my preferredSize attribute..
But removing the preferedSize attribute and changing the method createNodePlate() in the corresponding EditPart has done the trick for.